__________________________________________________________________________ T H E O L E R O E M E R M E S S E N G E R _______________________________________________ JJJJ C G JJJJJJ I E JJJJ __________________________________________________________________________ Newsletter of the International Jupiter Watch Satellite Discipline E-mail issue 15 March 24, 1995 Editor and Discipline Leader: John Spencer Voice: (602) 774-3358 Lowell Observatory Fax: (602) 774-6296 1400 W. Mars Hill Rd. Internet: spencer@lowell.edu Flagstaff, AZ 86001 ___________________________________________________________________________ EDITORIAL COMMENTS I'm including an important announcement from Bob Joseph regarding IRTF plans for Galileo support, a condensation and update of recent messages on Io's volcanic activity, and other recent Io observations, and news on upcoming (or not) Io workshops... Please send me material for inclusion in this newsletter when you have anything of general interest to the Jovian satellite community. If it's urgent and should go out separately rather than waiting for me to put out the next Ole Roemer, please let me know and I will do so. As the Galileo encounter approaches, would there be any interest in setting up an "exploder" so that mail sent to it would be automatically forwarded to everyone on this mailing list? John. ___________________________________________________________________________ IRTF PLANS FOR GALILEO SUPPORT A reminder that IRTF observing proposals for August 1995 - January 1996, including the period of the Galileo Jupiter orbit insertion, probe entry, and Io and Europa flybys on December 7th, are due on April 3rd. For more information, try the IRTF Online service, available by anonymous ftp to irtf.ifa.hawaii.edu, or the WWW site http://irtf.ifa.hawaii.edu The following message from Bob Joseph, outlining special IRTF plans for Galileo support, will appear in the next IRTF newsletter: The Galileo spacecraft makes its initial encounter with Jupiter on 7th December '95. The IRTF Division Chief, Bob Joseph, is announcing a regular sequence of monitoring observations of Jupiter and Io at the IRTF for the three months leading up to the encounter of Galileo with Jupiter. The plan is to obtain, in a service observing mode, a sequence of images of Jupiter and Io in a number of different filters using the facility infrared camera, "NSFCAM." The intent is to select a minimum number of diagnostic images at different wavelengths to provide the global context for interpretation of the spatially- and temporally-limited observations which the instruments on Galileo will produce. This should include studies of the atmosphere and ionosphere of Jupiter, and volcanic activity on Io. The plan is to define a minimum set of observations which will take no more than one hour per day to execute. These observations will be made in a nearly automatic fashion using the NSFCAM "Do file" feature. The entire sequence of observations can be programmed in a series of macros and executed by NSFCAM with a single command. This would be carried out by the IRTF telescope operator on duty at the beginning of every night for which NSFCAM is the instrument to be used by the scheduled observer. Since it is expected that these measurements will be made during twilight, they should have minimal impact on the scheduled observing program for the night. The images obtained in support of the Galileo encounter will be placed in an IRTF directory as they are taken. This archive will have full public access, so that the entire community can retrieve the images of Io and Jupiter and standards. A team consisting of Glenn Orton (JPL, for the Jovian atmosphere), John Spencer (Lowell Observatory, for Io or possibly the other satellites) and Steve Miller (University College London, for auroral or ionospheric observations), in their capacities as leaders of the International Jupiter Watch program, will make the final decisions on what program of measurements will be executed. Anyone wishing to suggest observations which should be made is encouraged to send a brief description of the measurement proposed and its scientific rationale. These suggestions may be sent to any of these three people, go@orton.Jpl.Nasa.Gov, spencer@lowell.edu, sm7@ib.rl.ac.uk, or to the IRTF Division Chief, Bob Joseph, at joseph@hubble.ifa.hawaii.edu. If this program proves successful, it may be continued in some form in the period following the inital encounter of Galileo with Jupiter. ___________________________________________________________________________ IO WORKSHOP STATUS Alfred McEwen and I have decided to shelve the idea of an "Io Predictions" workshop in Flagstaff this summer, and instead concentrate on planning an early post-Galileo Io meeting, probably sometime in the Fall of 1996. There is still likely to be a special "Io Predictions" issue of GRL, however- more details later. Rosaly Lopes (rlopes@jpluvs.jpl.nasa.gov), David Rothery (D.A.Rothery@open.ac.uk), and others are considering a focussed 1-day workshop before DPS on thermal remote sensing of volcanos on Io and the Earth, though the logistical feasibility has yet to be worked out. Contact them if you are interested. ___________________________________________________________________________ IO VOLCANIC ACTIVITY REPORT Since the last Ole Roemer, I have observed Io at various points in its orbit from 3 - 5 microns with NSFCAM at the IRTF on 3/1, 3/2, 3/8, 3/9, 3/10, and 3/11, have observed an eclipse and occultation of Io by Jupiter from 2.3 - 5 microns the IRTF on 3/14, and have imaged Io in Jupiter eclipse from 1.7 - 2.4 microns with OSIRIS at the Lowell 72" on 3/16 and 3/23. As noted in previous messages, we saw a bright hot spot against the sunlit disk from 3.5 - 4.8 microns on March 2nd: approximate location 45 S, 95 W, with a current uncertainty of about +/- 15 degrees, hopefully subject to improvement. It was comparable in flux to the sunlit disk at 4.8 microns, so it was not as bright as some previously observed outbursts. The location is not far from the fainter hot spot "Poliahu" noted by Goguen et al. in 1985 mutual event photometry, at 23 S, 81 W (+/- 5 degrees), but the position uncertainties probably don't overlap. 4.8 micron photometry of Io at high airmass on 2/28, two days before the outburst was noticed, suggests that Io's leading hemisphere may have been unusually bright then also, though the photometric precision is low. This would be interesting, as 5-micron outbursts in the past have appeared to last less than two days. A week later, on 3/9 and 3/11 we saw the same spot again in disk-resolved images, from 3.5 - 4.8 microns, but it was several times fainter than on 3/2. We may also have seen Pele in disk-resolved images on 3/8 and 3/10, but this is tentative. The Jupiter-facing side of Io was faint in Jupiter eclipse on 3/14 and 3/16, but as noted in an earlier message today, this morning (3/23 UT) it was approximately 8 (!) times brighter than the previous week at 2.3 microns and was also conspicuous at 1.7 microns. Unfortunately I do not have a location for the brightening, as I missed the Jupiter occultation disappearance. I will be attempting more Io eclipses and occultations by Jupiter at 1.7 and 2.3 microns with OSIRIS at the Lowell 72" on 3/30, 4/8, 4/15, 4/22, 4/24, 5/17, 5/24, 6/9, 6/11, 6/18, and 6/25 (July onwards is not yet scheduled). As mentioned in the last newsletter, Jay Goguen will be observing Io eclipses at the IRTF on 3/30 and 4/6, and I will be observing Io with NSFCAM at the IRTF on 4/13 and 4/15, so April is well covered. ___________________________________________________________________________ SPACE SHUTTLE OBSERVATIONS OF IO On March 4th, Paul Feldman (pdf@rowland.pha.jhu.edu) reported that: We observed it [Io] with HUT on Astro-2 this morning at eastern elongation. Good spectra but we don't have time for much analysis. Also observed at longer uv wavelengths by WUPPE. "HUT" is the Hopkins Ultraviolet Telescope. This was two days after the March 2nd outburst so this might give us a chance to see if the outburst affected the torus or neutral atmosphere. _______________________________________________________________________________ IO SODIUM OBSERVATIONS This from Larry Trafton (lmt@astro.as.utexas.edu), on 3/23: I have just finished a run looking at Io's NaD emissions with the CCD slit set North-South in the Jovian system. The dates were March 19-22, 1995 (UT) at McDonald Observatory. Strong and asymmetric emission was seen when Io was not far from elongation. Further examination is required to determine if the Na is more concentrated than usual. _______________________________________________________________________________ RECENT OR PENDING PUBLICATIONS Note the special issue of Science featuring papers on the comet crash which came out on March 3rd (vol. 267, 1237-1392). Hall, D.T., D.F. Strobel, P.D. Feldman, M.A. McGrath, and H.A. Weaver (1995). Detection of an oxygen atmosphere on Jupiter's moon Europa. Nature 373, 677-679. Blaney, D.L., T.V. Johnson, D.L. Matson, and G.J. Veeder (1995). Volcanic eruptions on Io: heat flow, resurfacing, and lava composition. Icarus 113, 220-225. Noll, K.S., H.A. Weaver, and A.M. Gonnella. The albedo spectrum of Europa from 2200 A to 3300 A. JGR Planets, in press.